In recognition of the ecological and cost impact of fossil fuels and other conventional energy sources, significant effort has been expended in developing methods for more efficient use of such energy sources. An important area of energy use for which greater energy efficiency is needed is the heating and cooling of spaces in which human activity is desired. Many approaches have been developed to decrease the amount heat transfer through the shell of such spaces. One of the most active and important areas of activity is the transfer of energy through fenestration where the activity has included use of window films or inserts, increasing the number of glazings per opening, and window treatments such as drapes, blinds, etc. While these approaches have shown considerable improvement in building energy efficiency, significant problems prevent more widespread and effective utilization.
Several problems exist in the approaches to minimizing heat transfer through fenestration. In particular for existing windows, it is desirable to maintain undistorted optical transparency, operation of the window treatments and windows and the aesthetics of the interior view of the window while providing thermal insulation. Furthermore, reuse of the insulating materials is highly desirable so that new materials do not need to be purchased each season. Supplemental windows known in the art either require the end user to customize one or more supplemental windows features to the dimensions of each window at the site of installation or are designed in ways that make size customization difficult in manufacturing.
When adding supplemental window features such as films, film support elements and window treatments, ease of installation (including measurement and fabrication), reusability and storage and aesthetics during and after use are very important while obtaining the thermal and radiation insulation desired. With window films intended for creating an additional “dead air” insulating layer adjacent to the window as well as window treatments, the dimension of the “dead air” space perpendicular to the window pane is subject to the film attachment areas that are generally dictated by existing features of the window and/or frame. In addition, such window films often must be mounted in such a way that inhibits the operability of non-fixed windows. Further, such window films are generally made for use only on the interior side of the window pane. Other window films, such as tints, infrared or ultraviolet reflective, or low-e films, generally adhere directly to the window pane and do not allow for simultaneous formation of an insulating layer.
Another problem with existing solutions is that most do not have any features designed to eliminate or reduce air flow or leakage around various elements of the window while maintaining operability of the window and associated window treatments with the supplemental window remaining in place. For example, it is common in sliding windows to have air leakage through the gaps between the jamb and the window frame, between the upper and lower sashes, between the sashes and the parts of the window frame that are in contact with them when in a closed state.
There is thus a need for a reduced cost frameless supplemental window that overcomes the disadvantages of prior art supplemental windows and that is effective at minimizing heat loss, retaining transparency and minimizing refractive index changes in the non-perimeter area of the window pane, is relatively simple to manufacture, prevents or minimizes air leakage between window elements, is easy to install and remove and does not impede the operability of the existing window.